Mercedes have admitted they're still in the dark as to why Lewis Hamilton suffered an engine failure at the Australian Grand Prix over the weekend.
The Briton had gone into the race hoping to climb up the leaderboard, having previously struggled in Bahrain and Saudi Arabia.
But Hamilton endured another day to forget, with the 39-year-old forced to withdraw from the race after 17 laps.
To compound Mercedes' woes, George Russell's crash on the penultimate lap meant the Silver Arrows were unable to add any points to their haul.
Lewis Hamilton and Mercedes have endured a nightmare start to the new F1 season
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Hamilton was bitterly disappointed after the race at Albert Park, with the veteran's final season with Mercedes failing to live up to the hype.
The team have now endured their worst start to an F1 season since 2012.
And technical director James Alisson, speaking in a new debrief video released by the team, has admitted Mercedes are still no closer to getting to the bottom of why their W15 vehicle failed.
"The power units will return to the safe hands of the guys at Brixworth, who will be able to figure out what let go," he said.
"All we know is the symptoms at the time, which was a rapid loss of oil pressure followed by a shutdown of the engine to protect it because when you know you've got catastrophic loss like that, the best thing you can do for the future is kill it there and then.
"And then you have not just got like a load of molten metal.
"You have normally got a fairly clear evidence chain of what caused it.
"And then that lets you work better for the future.
"So, we do not know yet, Brixworth and High Performance Powertrains will do in short order.
"And no doubt as soon as we know then they will jump in with their characteristic energy to make sure that any risk that happens on any other engine is mitigated as best we can."
Allison does, however, insist Mercedes' other foundations are 'in decent shape' ahead of the next race in Japan on April 7.
"We have drivers who are particularly good at keeping it on the island and our reliability overall is a strong point," he said.
"It is unusual to have a double DNF like that. It is certainly not something we expect to punctuate our season.
"What we are more focused on is the pace because if you get the pace sorted out the season will be okay whatever happens.
"The baseline reliability of the car, our procedural approach to it and the skill of our drivers will tend to keep you clear of DNFs.
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Mercedes are still in the dark over Lewis Hamilton's car problem that wrecked his hopes of Australian Grand Prix success
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"All our focus is on the pace knowing that those other foundations are in decent shape."
Hamilton, meanwhile, admitted Mercedes had a 'massive' problem on their hands trying to keep pace with Red Bull amid their abject displays this term.
Speaking after the race at Albert Park, he said: "I think the engine ceased.
"It just appeared out of nowhere, it was a split-second thing."
When asked about the difference between Mercedes and Red Bull, he added: "Oh it's a massive gap.
Lewis Hamilton crashed out of the Australian Grand Prix after just 17 laps
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"I think they have a second on us, something like that.
"He was on fresh tyres but the way he pulled away down the straight, I was like... Same as last year."